Conventional solenoids, such as those shown in prior art FIG. 1, have included a core design having four or more segments 12-18. One example of a prior art four segment solenoid core 10 includes a shell or frame 12, a bushing or journal 14, a plunger or armature 16, and a back stop or end cap 18. The four segment core design also includes at least two required air gaps 11,13. The working air gap 11 is located between the two magnetic pole faces forming the pole face geometry. The journal air gap 13 is located between the periphery of the plunger 16 and the bushing or journal 14.
During operation of the solenoid, magnetic flux 19(or magnetic lines of force) are transferred between the individual segments or core magnets, resulting in energy loss at the transfer points between segments. The transfer points include further unwanted air gaps at the interfaces 15, 17 between each of the multiple segments or pieces that are the equivalent of having resistors in series in an electrical circuit. Thus, conventional multiple segment solenoid cores often include several unwanted air gaps between each of the multiple segments 12-18 in addition to the required air gaps 11,13.
Accordingly, multiple segment solenoid cores are often not constructed for maximum efficiency. The increased efficiency of a solenoid is particularly important for applications in which solenoids are driven with low current electronics and/or with a battery as the supply voltage. Also, manufacturing costs increase with an increase in the number of segments or pieces that are required to make a tubular type solenoid. Accordingly, a tubular type solenoid is needed that lowers manufacturing costs while increasing the efficient conversion of electrical energy to mechanical work.